1. Field of the Invention
The present invention relates to a disc drive apparatus for playing or driving an information recording disc such as a magnetic disc.
2. Description of the Related Art
Hard disc drive (HDD) apparatus have prevailed as external memory devices for personal computers, and home-use electric/electronic appliances that have a built-in HDD are also marketed recently because recording density (or memory density) of HDD is improved and price reduction is realized. It is now possible to store a substantial amount of image and music contents in HDD so that products using HDD are manufactured one after another. Such products are expected to be incorporated in automobile audio sets, and it is assumed that most automobile navigation systems will be equipped with HDD although DVD is currently dominant.
Referring to FIG. 1 of the accompanying drawings, illustrated is a basic structure of HDD. The illustrated HDD is a ramp loading type wherein a magnetic head 51 located at a free end of an actuator 54 is mechanically caused to float from a magnetic disc surface.
As illustrated, the magnetic head 51 mounted on the actuator 54 is adapted to be able to move in a radial direction of a magnetic disc 53 (as indicated by the double arrow), and be positioned by a voice coil motor (VCM) 160. The magnetic head 51 is forced on the surface of the magnetic disc 53 with a resilient force of a suspension 57, but is controlled such that a gap of several tens of micrometers is created between the magnetic head 51 and the magnetic disc surface by an aerodynamic floating force acting on the magnetic head 51 produced upon rotations of the magnetic disc 53. When not operated, the magnetic head 51 is positioned at a retracted position, at which it rides on a tapered portion 56 of a ramp 55 formed at one end of a housing frame 50.
FIG. 2 is a cross sectional view illustrating positional relationship between the magnetic head 51 and ramp 55. As shown, the ramp 55 located in the vicinity of an outer periphery of the magnetic disc 53 has the tapered portion 56 that extends in a radially outward direction of the disc. This tapered portion 56 has a gentle inclination extending in a direction apart from the surface of the magnetic disc 53. The magnetic head 51 is located at a play position (position xe2x80x9caxe2x80x9d) above the magnetic disc 53 with a suitable clearance when it reads or writes information out of or into the magnetic disc 53 (i.e., drive condition). When not operated (unload condition), the magnetic head 51 moves over the tapered portion 56 and reaches the shunting position (or stand-by position) xe2x80x9cbxe2x80x9d as indicated by the arrow A.
The above described HDD apparatus is equipped with a function called xe2x80x9cemergency unloadxe2x80x9d. The emergency unload function forcibly moves the head to the retract position when a power supply to a motor for driving a spindle 52 and magnetic head 51 fails, in order to prevent the magnetic disc 53 from being damaged by the head. Although a power source is needed to perform the emergency unloading, it is known that when the power supply fails, a counter electromotive force generated by inertia rotations of the spindle motor 52, i.e., no load electromotive force, can be utilized to carry out the emergency unloading.
If the above described technique is applied to an engine-driven on-vehicle disc drive apparatus, the emergency unloading operation is executed every time the engine is started up since a battery voltage greatly drops upon starting up of the engine.
Referring to FIG. 3, illustrated is an example of a power source circuit employed in the engine-driven automobile. Specifically, an alternator G is driven by an engine (not shown). An AC power supplied from the alternator G is rectified and smoothed by a rectifier D and then fed to a battery B. A battery voltage Vb of the battery B is fed to a movable contact of an engine key switch SW. The engine key switch SW has stationary contacts ACC, ON and ST, and the battery voltage Vb passing through the contact ACC is supplied as an ACC power source to a light load LL such as an audio set. The battery voltage Vb passing through the contact ON is supplied as an ON power source to a heavy load HL such as power window. The battery voltage Vb passing through the contact ST is supplied as MST voltage to a starter motor (not shown) to rotate the starter motor and start the engine. The battery voltage Vb is also fed to the light load LL via a line BU as a back-up power source.
FIGS. 4A and 4B illustrate voltage changes in the power supply lines in the form of timing charts when the engine is started. Specifically, FIG. 4A illustrates the power source voltage for the back-up power source, and FIG. 4B illustrates the voltage change for the ACC. In these drawings, timing (I), (II), (III) and (IV) correspond to different positions of the engine key switch. Specifically, (I) indicates when the engine key is in the ACC position, which feeds electricity to the light load such as the audio equipments, (II) indicates when the engine key is in the ON position, which feeds electricity to the heavy load such as the power window device, (III) indicates when the engine key is in the ST position, which feeds electricity to the starter motor, and (IV) indicates when the engine key is returned to the ON position.
In this arrangement, not only the ACC voltage but also the back-up power supply drop in certain occasions because of the battery voltage drop upon starting of the engine (between (III) and (IV) in FIGS. 4A and 4B).
When, therefore, the above described HDD is employed in an engine-driven vehicle, the emergency unload operation likely takes place every time the engine is started, because of voltage drop upon starting of the engine. Since, as mentioned above, the emergency unloading takes advantage of counter electromotive force of the spindle motor and forcibly causes the head to move, the magnetic head 51 in a product used for a vehicle has more chances to collide against the taper portion 56 of the ramp 55 while it is moving to the shunting position xe2x80x9cbxe2x80x9d of the ramp 55 than a product such as personal computer used for other than the vehicle. In other words, the ramp 55 and magnetic head 51 in the HDD apparatus used for the vehicle need to have improved durability.
This is a common problem in the HDD apparatus operated under an unstable power supply.
The present invention is conceived in view of the above described problems, and has an object to provide a disc drive apparatus that does not have shortened durability even if operated under an unstable power supply.
In order to solve the above-mentioned problem, there is provided a disc drive apparatus adapted to write and/or read information into and/or from an information recording disc, with the information recording disc being rotated by a rotary drive motor and a head drive being controlled to position a head in a radial direction of the information recording disc under supply of predetermined rated power source voltage, comprising: a forcible restoration device for controlling the head drive to execute a forcible restoration action that forcibly moves the head to a shunting position when the power source voltage drops below a predetermined threshold value; a detection and count device for detecting execution of the forcible restoration action, counting how many times the forcible restoration action is executed, and updating a count value every time execution of the forcible restoration action is detected; and a notification device for notifying an updated count value.
With the arrangements mentioned above, times of the emergency unloading occurs are monitored and informed to a user through a display, for example, so that the user is notified of an operating condition of a disc drive apparatus and the user""s attention is drawn to when the disc drive apparatus should be replaced and the like. This improves reliability of the disc drive apparatus as a recorded information reproducing apparatus. Even if further, a power supply to the disc drive apparatus is interrupted, it is possible to insure the emergency unloading operation to occur by using a counter electromotive force generated because of inertia rotations of a recording medium and drive means. Moreover, notification and caution to the user is made with different colors depending upon how many times a forced movement occurs so that the user is more effectively notified of when the user should replace the disc drive apparatus and the like. Use of different colors has a greater impact on the user.